1. Field of the Invention
The present invention relates to electronic keyboard controls for processing machines and, more particularly, to a keyboard switch assembly which is equipped with a touch-centering grid and and a printed circuit board and which is adapted for mounting in the control panel of a processing machine.
2. Description of the Prior Art
Keyboard switch assemblies consisting of a matrix of horizontal and vertical rows of depressible switches are commonly used on electronic calculators and, more recently, in connection with push button telephones.
The application of computers and numerical controls to industrial processing machines has made it necessary to replace the customary push buttons and adjustable dials with keyboard switch assemblies for both numerical input and operational control input. Thus, a modern injection molding machine, for example, may have a central control panel with separate keyboards for program input, central operational control input, and separate manual control input.
Experience has shown that, when such a complex processing machine is operated by a less than fully qualified machine operator, input mistakes may be made which range from erroneous data and resulting defective product output to erroneous operational commands and resulting potentially serious damage to the machine. Problems of this kind are not uncommon in less industrialized countries which lack the required pool of skilled technicians, and where an inadequately trained or otherwise unreliable person may be called upon to operate a complex machine.